Self-soldering heat-coil fuse for switchboard protection



H, F. SKIDMORE SELF SOLDERING HEAT COIL FUSE FOR SWITQHBOARD PROTECTIONFiled March 25, 1927 Patented Dec. 24, 1929 UNITED STATES;

PATENT OFFICE HENRY I. SKIDMORE, OF CHIGAGQAILLINOIS, ASSIGNOI TOELECTRIC 00.,

OF-CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS Y BELF-SOLDERIIIGHEAT-COIL FUSE FOB SVVITCIIIBOAIBID PROTECTION a lication filed March25, 192i. Serial No. 17am.

My invention relates to thermal protective devices adapted to beinserted in an' electric circuit for breaking the circuit when anexcessive amount of current flows in the circuit. I

More particularly my invention relates to the type of thermal protectorknown as a heat coil fuse wherein current in the circuit passes througha coil in the fuse and heats a portion of the device, the heating ofthis portion above a certain temperature causing the device to open thecircuit.

It is a purpose of the invention to apply fuses of this character whichmaybe rea ily re-set by hand after it has been opened without removingthe fuse from its mounting and without heating it up or using anyparticular tools.

Another purpose of this invention is to rovide a fuse of this characterwhich may, y manual operation, be caused to open the circuit regardlessof the amount of current flowing in said circuit.

Other objects and advantages of the invention will appear when taken inconnection 7 with the accompanying drawings. However, I wish it to bedistinctly understood that I do not intend to limit myself to the exactdetails shown and described, but that I intend to avail myself of allsuch modifications as would occur to one skilled in this art and.

as would fall within the scope of the claims.

In the drawings:

Fig. 1 is a sectional view taken longitudinally through the device;'andI Fig. 2 is a detail view illustratin the engagement between electrodesof the use,

Referring now in detail to the drawings,

the numeral 5 indicates an elongated shell which may be of any suitableinsulatin terial, such for instance as glass, an this shell is providedat its opposite ends with the terminal members ,6 and 7, which as shown,fit down over the, ends of the shell and maybe secured thereon by anysuitablecement or other means. Within the terminal 6, I provide theinsulating washer 8 which is held in engagement with the end of theshell 5 by the terminal and which carries the inwardly extending rod orstem 9. This stem as shown has a squared shank portion extending throughthe washer 8 and at theouter end thereof is soldered down againstthemetal washer 11 by means of the solder 12. This structure retains thestem 9 rigidly in place and prevents rotation thereof relative to thewasher 8. To further prevent any loosenin of the washer 8 within theterminal 6, preferably fill thespace around the washer 11 and solder 12with a suitable cement as illustrated at 13.

A conductor extends from the tip 14 of the terminal 6 inwardly throughan opening in the washer 8 and is coiled around the stem 9 as shown at15 to provide a heating coil which, upon passage of currenttherethrough, will heat the stem 9. The end of this conductor is thenpassed through the washer 8 in the opposite direction and is secured inthe solder 12.

From this point the circuit extends through the stem 9 to the ratchetwheel 16 which, as illustrated, is pivotallymounted in the slotted end17 of the stem 9. This wheel is provided before assembly with aplurality of openings indicated at 18 and these openmgs are filled withthe suitable soft solder having a desired melting point and the Wheel issoldered in place so that when the stem 9 is heated up, the solder willsoften and release the ratchet 16 to permit it to be turned. When thestem 9 cools after the circuit is broken, the wheel 16 is again solderedagainst rotation by means of the solder in the holes 18in contact withboth the wheel and the stem. v

The otherfelectrode'for completing the circuit' consists of the strip,19 having the slot 20 therein, which slot is adapted to receive the edgeof the wheel 16 and thus hook the member 19 over the teeth of the wheel.The strip 19 is formed integral with the tubular member 21 which extendsoutwardly through the open end of the terminal 7 and projects slightlythereheyond when the electrodes 16 and 19 are in contact. The stem 21 asshown, is rather loosely mounted, as shown at 22, in. the end of theterminal 7 so as to permit it to rock back and forth and in this mannerbe manipulated to engage the strip 19 with the ratchet wheel 16. I, i

To provide meansfor withdrawing the electrode 19 and opening thecircuitautomatically when the stem 9 is heated so as to permit rotation of thewheel 16, I provide the spring 23, which as shown, is soldered by"spring withdraws the electrode 19 away from e wheel 16 to open a widegap in the circuit and retains it in this position until it is againclosed by pushing the rod 21 inwardly and manipulating it so as toengage slot 20 over the ratchet teeth of the wheel 16. When this isdone, the fuse is again in condition for further use.

The advantages of this structure,-it is thought, will be readilyapparent from the above description since it provides a fuse which'maybe reset any indefinite number of times after opening the circuit bymerely pressing in on the rod 21 without removing the tubefrom itsmounting or in any way disturbing its use. Furthermore, if it is desiredto open a circuit for any particular purpose, this may be done bymanipulating the rod 21 to release the electrode 19 from the wheel 16 soas to make it unnecessary to remove the fuse or overheat it to separatethe electrodes. The fuse in this way 'acts somewhat as a switch whichmay be manually operated.

Having thus described my invention, what I claim-as new and desire tosecure by U. S. Letters Patent is:

1. A thermal protector of the character described comprising a pair ofelectrodes, heat j responsive means normally retaining said electrodesin electrical engagement and adapted upon undue increase in heat topermit separation of said electrodes, spring means normally under stressadapted to cause a wide separation of said electrodes upon softening ofsaid heat responsive means, an

enclosing shell housing said electrodes, heat responsive means andspring means, and

. means projecting outside said shell for again setting said electrodesinto operative engagement without re-softening said heat responsivemeans, said means projecting outside the shell also being manuallyoperable to disjacent one of said terminals, said electrode comprising astem having a ratchet wheel rotatably secured thereto, heat responsivemeans normally preventing rotation of said wheel. but adapted upon undueincrease in heat to permit rotation thereof, a second electrode normallyengaging said ratchet wheel but releasable therefrom'on rotation of saidwheel, and'a spring normally under stress adaptedto rotate said wheeland separate said electrodes upon softening said heat responsive means.H

" 3. A thermal protector of the character described comprising anenclosing shell having terminals at opposite ends-thereof, an electroderigidly secured to said shell. adjacent one of said terminals, saidelectrode comprising. a-stem having a ratchet wheel rotatably securedthereto, heat responsive means normally preventing rotation of saidwheel but adapted upon undue increase in heat to permit rotationthereof, a second electrode normallyengaging said ratchet wheel butreleasable therefrom on rotation of said wheel, a spring normally understress adapted to rotate said wheel and. separate said electrodes uponsoftening said heat responsive means, and ano erating member connectedwith said second electrode 'projectin externally of said shell forre-setting said second electrode in engagement with said ratchet wheel.

ice

4. A- thermal protector of the character described comprising anenclosing shell having terminals at opposite ends thereof, anelectrode'rigidly secured to said shell adjacent one of said terminals,said electrode comprising a stem;ha'ving a ratchet wheel rotatablysecured thereto, heat responsive means normally preventing rotation ofsaid wheel but adapted upon nndue'increase in heat to permit rotationthereof, a second electrode normally engaging said ratchet wheel butreleasable therefrom on rotation of said wheel, and a spring normallyunder stress adapted to rotate said wheel and separate said electrodesupon softening said heat responsive means,- said spring electricallyconnecting said second electrode with the other of said terminals.

5. A thermal protector of the character described comprising. anenclosing shell having terminals at opposite ends thereof,

an electrode rigidly secured to said shell ad jacent one of saidterminals, said electrode comprising a stem havingfa ratchetwheelrotatably secured; thereto, heatresponsive means normallypreventing rotation of said wheel but adapted upon'u'ndue increase inheat to permit rotation thereof, a second electrode normally engagingsaid ratchet wheel but releasable therefrom on rotation of said Wheel,and a spring normally under stress adapted to rotate said Wheel andseparate said electrodes upon softening said heat responsive means, saidspring electrically connecting said second electrode with the other ofsaid terminals, and an operating member projecting from said secondeleetrodethrough said last named terminal for manually engaging orseparating said electrodes.

1n witness whereof, I hereunto subscribe my7name this 25th day ofFebruary, A. D 192 HENRY F. SKIDMORE.

